This section introduces aspects that may help facilitate a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
The rapidly increasing demand for mobile data applications coupled with limited licensed spectrum availability has led to significant interest in the deployment of heterogeneous networks comprising mixtures of macro-cells and small cells operating in the same spectrum. Such networks often exhibit relatively poor performance on the downlink because of the interference caused by macro-cell transmissions to those from small cells. Judicious resource partitioning schemes have been shown to mitigate the interference problem, leading to significant improvement in the edge and median throughput in heterogeneous networks. However, it is, typically, only static or near-static users that can avail of this improvement; users with a high degree of mobility do not benefit from the high bandwidth made available by the heterogeneous networks because of the following reason: They are either forced to remain connected to macro-cells in order to avoid frequent handoffs, which means they cannot make use of the extra bandwidth that is typically available only with the small cells, or, if they are allowed to connect to small cells, the frequent handoffs that ensue preclude their getting a consistently high level of throughput. Consequently, there is likely to be a clear difference in the quality of experience for static (or near-static) users and highly mobile users of heterogeneous networks.
The best known solution to avoid the frequent hard handoffs between different base stations is to permit soft handoffs where a mobile user maintains links with multiple base stations at the same time. If a mobile user is in soft handoff with a set of base stations, downlink transmissions to the mobile user are carried synchronously (in an identical manner) by all of the base stations involved in the soft handoff. In such an arrangement, the performance associated with the downlink connection to the mobile user is more-or-less determined by the base station that has the strongest link to the mobile user. While soft handoff may alleviate some of the problems experienced by highly mobile users, it has several limitations. For example, soft handoffs are not available in several networks, e.g. those based on the 3GPP LTE standard. Also, they typically lead to a loss of capacity for data-oriented networks since they require multiple base stations to carry replicas of the same data. Finally, if resources are partitioned between macro-cells and small cells in order to avoid certain interference-related problems, it will not be possible to implement soft handoffs between macro-cells and small cells. Taking all of these points into account, it is clear that soft handoffs do not offer a viable solution to the problem being addressed.
Thus, new solutions and techniques that are able to enable even highly mobile users of heterogeneous networks to experience improved performance would meet a need and advance wireless communications generally.
Specific embodiments of the present invention are disclosed below with reference to FIGS. 1-4. Both the description and the illustrations have been drafted with the intent to enhance understanding. For example, the dimensions of some of the figure elements may be exaggerated relative to other elements, and well-known elements that are beneficial or even necessary to a commercially successful implementation may not be depicted so that a less obstructed and a more clear presentation of embodiments may be achieved. In addition, although the logic flow diagrams above are described and shown with reference to specific steps performed in a specific order, some of these steps may be omitted or some of these steps may be combined, sub-divided, or reordered without departing from the scope of the claims. Thus, unless specifically indicated, the order and grouping of steps is not a limitation of other embodiments that may lie within the scope of the claims.
Simplicity and clarity in both illustration and description are sought to effectively enable a person of skill in the art to make, use, and best practice the present invention in view of what is already known in the art. One of skill in the art will appreciate that various modifications and changes may be made to the specific embodiments described below without departing from the spirit and scope of the present invention. Thus, the specification and drawings are to be regarded as illustrative and exemplary rather than restrictive or all-encompassing, and all such modifications to the specific embodiments described below are intended to be included within the scope of the present invention.